Shape selective reactions with zeolite catalyst modified with group IVB metal

ABSTRACT

A process for the conversion of aromatic compounds to dialkylbenzene compounds rich in the 1,4-dialkylbenzene isomer. The reaction is carried out in the presence of a particular type of zeolite catalyst having a silica to alumina mole ratio of at least 12 and a constraint index of about 1-12, said catalyst having been modified by treatment with compounds of germanium, tin and/or lead, and optionally phosphorus, to deposit a minor proportion of such elements on the zeolite.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention disclosed herein relates to the production ofdialkylbenzene compounds utilizing a modified crystalline zeolitecatalyst to yield a product mixture in which the 1,4-dialkylbenzeneisomer is substantially in excess of its normal equilibriumconcentration.

2. Description of the Prior Art

The disproportionation of aromatic hydrocarbons in the presence ofzeolite catalysts has been described by Grandio et al. in the OIL ANDGAS JOURNAL, Vol. 69, Number 48(1971).

U.S. Pat. Nos. 3,126,422; 3,413,374; 3,598,878; 3,598,879 and 3,607,961show vapor-phase disproportionation of toluene over various catalysts.

In these prior art processes, the dimethylbenzene product produced hasthe equilibrium composition of approximately 24 percent of 1,4-, 54percent of 1,3- and 22 percent of 1,2-isomer. Of the dimethylbenzeneisomers, 1,3-dimethylbenzene is normally the least desired product, with1,2- and 1,4-dimethylbenzene being the more useful products.1,4-Dimethylbenzene is of particular value, being useful in themanufacture of terephthalic acid which is an intermediate in themanufacture of synthetic fibers such as "Dacron". Mixtures ofdimethylbenzene isomers, either alone or in further admixture withethylbenzene, have previously been separated by expensivesuperfractionation and multistage refrigeration steps. Such process, aswill be realized, involves high operation costs and has a limited yield.

Various modified zeolite catalysts have been developed to alkylate ordisproportionate toluene with a greater or lesser degree of selectivityto 1,4-dimethylbenzene isomer. Hence, U.S. Pat. Nos. 3,972,832,4,034,053, 4,128,592 and 4,137,195 disclose particular zeolite catalystswhich have been treated with compounds of phosphorus and/or magnesium.Boron-containing zeolites are shown in U.S. Pat. No. 4,067,920 andantimony-containing zeolites in U.S. Pat. No. 3,979,472. Similarly, U.S.Pat. Nos. 3,965,208 and 4,117,026 disclose other modified zeolitesuseful for shape selective reactions.

While the above-noted prior art is considered of interest in connectionwith the subject matter of the present invention, the conversion processdescribed herein, utilizing a crystalline zeolite catalyst of specifiedcharacteristics which has undergone the particular treatment disclosed,has not, insofar as is known, been previously described.

SUMMARY OF THE INVENTION

In accordance with the present invention, there has now been discovereda novel process for conversion of organic compounds (e.g., hydrocarboncompounds) in the presence of a particular type of modified zeolitecatalyst. An especially advantageous element of the invention comprisesthe selective production of the 1,4-isomer of dialkylated benzenecompounds. The process involves contacting an alkylated aromaticcompound, either alone or in admixture with a suitable alkylating agentsuch as methanol or ethylene, with particular type of modifiedcrystalline zeolite catalyst and under suitable conversion conditioningto effect disproportionation or transalkylation of alkylbenzenecompounds or alkylation of aromatic compounds to selectively produce the1,4-dialkylbenzene isomer in excess of its normal equilibriumconcentration.

The particular type of crystalline zeolite catalysts utilized herein arezeolite materials having a silica to alumina ratio of at least about 12,a constraint index within the approximate range of 1 to 12 and whichhave been modified by initial treatment with a compound derived from oneor more of the metals of Group IVB of the Periodic Table of Elements(i.e. Ge, Sn and Pb) to yield a composite containing a minor proportionof an oxide of such metal. In addition to treatment of the zeolite withthe germanium, tin or lead containing compound, the zeolite may also betreated with a phosphorus-containing compound to deposit a minorproportion of an oxide of phosphorus thereon in addition to the oxide ofthe Group IVB metal.

An embodiment of the disclosed invention is a process for the alkylationof aromatic compounds, in the presence of the herein described modifiedzeolite catalysts, with selective production of the 1,4-dialkylbenzeneisomer in preference to the 1,2- and 1,3-isomers thereof. Especiallypreferred embodiments involve the selective production of1,4-dimethylbenzene from toluene and methanol and1-ethyl-4-methylbenzene from toluene and ethylene.

Another embodiment contemplates the selective disproportionation ortransalkylation of alkylbenzene and polyalkylbenzene compounds in thepresence of the disclosed catalysts, thereby yielding 1,4-disubstitutedbenzenes in excess of their normal equilibrium concentration. Forexample, under appropriate conditions of temperature and pressure,toluene will disproportionate in the presence of these catalysts toproduce benzene and dimethylbenzenes rich in the desirable 1,4-isomer.

DESCRIPTION OF SPECIFIC EMBODIMENTS

The crystalline zeolites utilized herein are members of a novel class ofzeolitic materials which exhibit unusual properties. Although thesezeolites have unusually low alumina contents, i.e. high silica toalumina mole ratios, they are very active even when the silica toalumina mole ratio exceeds 30. The activity is surprising sincecatalytic activity is generally attributed to framework aluminum atomsand/or cations associated with these aluminum atoms. These zeolitesretain their crystallinity for long periods in spite of the presence ofsteam at high temperature which induces irreversible collapse of theframework of other zeolites, e.g. of the X and A type. Furthermore,carbonaceous deposits, when formed, may be removed by burning at higherthan usual temperatures to restore activity. These zeolites, used ascatalysts, generally have low coke-forming activity and therefore areconducive to long times on stream between regenerations by burningcarbonaceous deposits with oxygen-containing gas such as air.

An important characteristic of the crystal structure of this novel classof zeolites is that it provides a selective constrained access to andegress from the intracrystalline free space by virtue of having aneffective pore size intermediate between the small pore Linde A and thelarge pole Linde X, i.e. the pore windows of the structure are of abouta size such as would be provided by 10-membered rings of silicon atomsinterconnected by oxygen atoms. It is to be understood, of course, thatthese rings are those formed by the regular disposition of thetetrahedra making up the anionic framework of the crystalline zeolite,the oxygen atoms themselves being bonded to the silicon (or aluminum,etc.) atoms at the centers of the tetrahedra.

The silica to alumina mole ratio referred to may be determined byconventional analysis. This ratio is meant to represent, as closely aspossible, the ratio in the rigid anionic framework of the zeolitecrystal and to exclude aluminum in the binder or in cationic or otherform within the channels. Although zeolites with a silica to aluminamole ratios of at least 12 are useful, it is preferred in some instancesto use zeolites having substantially higher silica/alumina ratios, e.g.1600 and above. In addition, zeolites as otherwise characterized hereinbut which are substantially free of aluminum, that is zeolites havingsilica to alumina mole ratios of up to infinity, are found to be usefuland even preferable in some instances. Such "high silica" or "highlysiliceous" zeolites are intended to be included within this description.Also to be included within this definition are substantially pure silicaanalogs of the useful zeolites described herein, that is to say thosezeolites having no measurable amount of aluminum (silica to alumina moleratio of infinity) but which otherwise embody the characteristicsdisclosed.

The novel class of zeolites, after activation, acquire anintracrystalline sorption capacity for normal hexane which is greaterthan that for water, i.e. they exhibit "hydrophobic" properties. Thishydrophobic character can be used to advantage in some applications.

The novel class of zeolites useful herein have an effective pore sizesuch as to freely sorb normal hexane. In addition, the structure mustprovide constrained access to larger molecules. It is sometimes possibleto judge from a known crystal structure whether such constrained accessexists. For example, if the only pore windows in a crystal are formed by8-membered rings of silicon and aluminum atoms, then access by moleculesof larger cross-section than normal hexane is excluded and the zeoliteis not of the desired type. Windows of 10-membered rings are preferred,although in some instances excessive puckering of the rings or poreblockage may render these zeolites ineffective.

Although 12-membered rings in theory would not offer sufficientconstraint to produce advantageous conversions, it is noted that thepuckered 12-ring structure of TMA offretite does show some constrainedaccess. Other 12-ring structures may exist which may be operative forother reasons and, therefore, it is not the present intention toentirely judge the usefulness of a particular zeolite solely fromtheoretical structural considerations.

Rather than attempt to judge from crystal structure whether or not azeolite possesses the necessary constrained access to molecules oflarger cross-section than normal paraffins, a simple determination ofthe "Constraint Index" as herein defined may be made by passingcontinuously a mixture of an equal weight of normal hexane and3-methylpentane over a sample of zeolite at atmospheric pressureaccording to the following procedure. A sample of the zeolite, in theform of pellets or extrudate, is crushed to a particle size about thatof coarse sand and mounted in a glass tube. Prior to testing, thezeolite is treated with a stream of air at 540° C. for at least 15minutes. The zeolite is then flushed with helium and the temperature isadjusted between 290° C. and 510° C. to give an overall conversion ofbetween 10% and 60%. The mixture of hydrocarbons is passed at 1 liquidhourly space velocity (i.e., 1 volume of liquid hydrocarbon per volumeof zeolite per hour) over the zeolite with a helium dilution to give ahelium to (total) hydrocarbon mole ratio of 4:1. After 20 minutes onstream, a sample of the effluent is taken and analyzed, mostconveniently by gas chromatography, to determine the fraction remainingunchanged for each of the two hydrocarbons.

While the above experimental procedure will enable one to achieve thedesired overall conversion of 10 to 60% for most zeolite samples andrepresents preferred conditions, it may occasionally be necessary to usesomewhat more severe conditions for samples of very low activity, suchas those having an exceptionally high silica to alumina mole ratio. Inthose instances, a temperature of up to about 540° C. and a liquidhourly space velocity of less than one, such as 0.1 or less, can beemployed in order to achieve a minimum total conversion of about 10%.

The "Constraint Index" is calculated as follows: ##EQU1##

The Constraint Index approximates the ratio of the cracking rateconstants for the two hydrocarbons. Zeolites suitable for the presentinvention are those having a Constraint Index of 1 to 12. ConstraintIndex (CI) values for some typical materials are:

    ______________________________________                                                          C.I.                                                        ______________________________________                                        ZSM-4               0.5                                                       ZSM-5               8.3                                                       ZSM-11              8.7                                                       ZSM-12              2                                                         ZSM-23              9.1                                                       ZSM-35              4.5                                                       ZSM-38              2                                                         ZSM-48              3.4                                                       TMA Offretite       3.7                                                       Clinoptilolite      3.4                                                       Beta                0.6                                                       H-Zeolon (mordenite)                                                                              0.4                                                       REY                 0.4                                                       Amorphous Silica-Alumina                                                                          0.6                                                       Erionite            38                                                        ______________________________________                                    

The above-described Constraint Index is an important and even criticaldefinition of those zeolites which are useful in the instant invention.The very nature of this parameter and the recited technique by which itis determined, however, admit of the possibility that a given zeolitecan be tested under somewhat different conditions and thereby exhibitdifferent Constraint Indices. Constraint Index seems to vary somewhatwith severity of operation (conversion) and the presence or absence ofbinders. Likewise, other variables such as crystal size of the zeolite,the presence of occluded contaminants, etc., may affect the constraintindex. Therefore, it will be appreciated that it may be possible to soselect test conditions as to establish more than one value in the rangeof 1 to 12 for the Constraint Index of a particular zeolite. Such azeolite exhibits the constrained access as herein defined and is to beregarded as having a Constraint Index in the range of 1 to 12. Alsocontemplated herein as having a Constraint Index in the range of 1 to 12and therefore within the scope of the defined novel class of highlysiliceous zeolites are those zeolites which, when tested under two ormore sets of conditions within the above-specified ranges of temperatureand conversion, produce a value of the Constraint Index slightly lessthan 1, e.g. 0.9, or somewhat greater than 12, e.g. 14 or 15, with atleast one other value within the range of 1 to 12. Thus, it should beunderstood that the Constraint Index value as used herein is aninclusive rather than an exclusive value. That is, a crystalline zeolitewhen identified by any combination of conditions within the testingdefinition set forth herein as having a Constraint Index in the range of1 to 12 is intended to be included in the instant novel zeolitedefinition whether or not the same identical zeolite, when tested underother of the defined conditions, may give a Constraint Index valueoutside of the range of 1 to 12.

The novel class of zeolites defined herein is exemplified by ZSM-5,ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38, ZSM-48 and other similarmaterials.

ZSM-5 is described in greater detail in U.S. Pat. No. 3,702,886 and No.Re 29,948. The entire descriptions contained within those patents,particularly the X-ray diffraction pattern of therein disclosed ZSM-5,are incorporated herein by reference.

ZSM-11 is described in U.S. Pat. No. 3,709,979. That description, and inparticular the X-ray diffraction pattern of said ZSM-11, is incorporatedherein by reference.

ZSM-12 is described in U.S. Pat. No. 3,832,449. That description, and inparticular the X-ray diffraction pattern disclosed therein, isincorporated herein by reference.

ZSM-23 is described in U.S. Pat. No. 4,076,842. The entire contentthereof, particularly the specification of the X-ray diffraction patternof the disclosed zeolite, is incorporated herein by reference.

ZSM-35 is described in U.S. Pat. No. 4,016,245. The description of thatzeolite, and particularly the X-ray diffraction pattern thereof, isincorporated herein by reference.

ZSM-38 is more particularly described in U.S. Pat. No. 4,046,859. Thedescription of that zeolite, and particularly the specified X-raydiffraction pattern thereof, is incorporated herein by reference.

ZSM-48 can be identified, in terms of moles of anhydrous oxides per 100moles of silica, as follows:

(0-15)RN:(0-1.5)M_(2/n) O:(0-2)Al₂ O₃ :(100)SiO₂

wherein M is at least one cation having a valence n; and RN is a C₁ -C₂₀organic compound having at least one amine functional group of pK_(a)≧7.

It is recognized that, particularly when the composition containstetrahedral, framework aluminum, a fraction of the amine functionalgroups may be protonated. The doubly protonated form, in conventionalnotation, would be (RNH)₂ O and is equivalent in stoichiometry to 2RN+H₂O.

The characteristic X-ray diffraction pattern of the synthetic zeoliteZSM-48 has the following significant lines:

    ______________________________________                                        Characteristic Lines of ZSM-48                                                d(A)       Relative Intensity                                                 ______________________________________                                        11.9       W-S                                                                10.2       W                                                                  7.2        W                                                                  5.9        W                                                                  4.2        VS                                                                 3.9        VS                                                                 3.6        W                                                                  2.85       W                                                                  ______________________________________                                    

These values were determined by standard techniques. The radiation wasthe K-alpha doublet of copper, and a scintillation counter spectrometerwith a strip chart pen recorder was used. The peak heights, I, and thepositions as a function of 2 times theta, where theta is the Braggangle, were read from the spectrometer chart. From these, the relativeintensities, 100 I/I_(o), where I_(o) is the intensity of the strongestline or peak, and d (obs.), the interplanar spacing in A, correspondingto the recorded lines, were calculated. In the foregoing table therelative intensities are given in terms of the symbols W=weak, VS=verystrong and W-S=weak-to-strong. Ion exchange of the sodium ion withcations reveals substantially the same pattern with some minor shifts ininterplanar spacing and variation in relative intensity. Other minorvariations can occur depending on the silicon to aluminum ratio of theparticular sample, as well as if it has been subjected to thermaltreatment.

The ZSM-48 can be prepared from a reaction mixture containing a sourceof silica, water, RN, an alkali metal oxide (e.g. sodium) and optionallyalumina. The reaction mixture should have a composition, in terms ofmole ratios of oxides, falling within the following ranges:

    ______________________________________                                        Reactants       Broad       Preferred                                         ______________________________________                                        Al.sub.2 O.sub.3 /SiO.sub.2                                                                 =     0 to 0.02   0 to 0.01                                     Na/SiO.sub.2  =     0 to 2      0.1 to 1.0                                    RN/SiO.sub.2  -     0.01 to 2.0 0.05 to 1.0                                   OH.sup.- /SiO.sub.2                                                                         =     0 to 0.25   0 to 0.1                                      H.sub.2 O/SiO.sub.2                                                                         =     10 to 100   20 to 70                                      H.sup.+ (added)/SiO.sub.2                                                                   =     0 to 0.2    0 to 0.05                                     ______________________________________                                    

where RN is a C₁ -C₂₀ organic compound having amine functional group ofpK_(a) ≧7. The mixture is maintained at 80°-250° C. until crystals ofthe material are formed. H⁺ (added) is moles acid added in excess of themoles of hydroxide added. In calculating H⁺ (added) and OH values, theterm acid (H⁺) includes both hydronium ion, whether free or coordinated,and aluminum. Thus aluminum sulfate, for example, would be considered amixture of aluminum oxide, sulfuric acid, and water. An aminehydrochloride would be a mixture of amine and HCl. In preparing thehighly siliceous form of ZSM-48 no alumina is added. Thus, the onlyaluminum present occurs as an impurity in the reactants.

Preferably, crystallization is carried out under pressure in anautoclave or static bomb reactor, at 80° C. to 250° C. Thereafter, thecrystals are separated from the liquid and recovered. The compositioncan be prepared utilizing materials which supply the appropriate oxide.Such compositions include sodium silicate, silica hydrosol, silica gel,silicic acid, RN, sodium hydroxide, sodium chloride, aluminum sulfate,sodium aluminate, aluminum oxide, or aluminum itself. RN is a C₁ -C₂₀organic compound containing at least one amine functional group ofpK_(a) ≧7, as defined above, and includes such compounds as C₃ -C₁₈primary, secondary, and tertiary amines, cyclic amine (such aspiperidine, pyrrolidine and piperazine), and polyamines such as NH₂--C_(n) H_(2n) --NH₂ wherein n is 4-12.

The original cations can be subsequently replaced, at least in part, bycalcination and/or ion exchange with another cation. Thus, the originalcations are exchanged into a hydrogen or hydrogen ion precursor form ora form in which the original cations has been replaced by a metal ofGroups II through VIII of the Periodic Table. Thus, for example, it iscontemplated to exchange the original cations with ammonium ions or withhydronium ions. Catalytically active forms of these would include, inparticular, hydrogen, rare earth metals, aluminum, manganese and othermetals of Groups II and VIII of the Periodic Table.

It is to be understood that by incorporating by reference the foregoingpatents to describe examples of specific members of the novel class withgreater particularity, it is intended that identification of the thereindisclosed crystalline zeolites be resolved on the basis of theirrespective X-ray diffraction patterns. As discussed above, the presentinvention contemplates utilization of such catalysts wherein the moleratio of silica to alumina is essentially unbounded. The incorporationof the identified patents should therefore not be construed as limitingthe disclosed crystalline zeolites to those having the specificsilica-alumina mole ratios discussed therein, it now being known thatsuch zeolites may be substantially aluminum-free and yet, having thesame crystal structure as the disclosed materials, may be useful or evenpreferred in some applications. It is the crystal structure, asidentified by the X-ray diffraction "fingerprint", which establishes theidentity of the specific crystalline zeolite material.

The specific zeolites described, when prepared in the presence oforganic cations, are substantially catalytically inactive, possiblybecause the intracrystalline free space is occupied by organic cationsfrom the forming solution. They may be activated by heating in an inertatmosphere at 540° C. for one hour, for example, followed by baseexchange with ammonium salts followed by calcination at 540° C. in air.The presence of organic cations in the forming solution may not beabsolutely essential to the formation of this type zeolite; however, thepresence of these cations does appear to favor the formation of thisspecial class of zeolite. More generally, it is desirable to activatethis type catalyst by base exchange with ammonium salts followed bycalcination in air at about 540° C. for from about 15 minutes to about24 hours.

Natural zeolites may sometimes be converted to zeolite structures of theclass herein identified by various activation procedures and othertreatments such as base exchange, steaming, alumina extraction andcalcination, alone or in combinations. Natural minerals which may be sotreated include ferrierite, brewsterite, stilbite, dachiardite,epistilbite, heulandite, and clinoptilolite.

The preferred crystalline zeolites for utilization herein include ZSM-5,ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38, and ZSM-48, with ZSM-5 beingparticularly preferred.

In a preferred aspect of this invention, the zeolites hereof areselected as those providing among other things a crystal frameworkdensity, in the dry hydrogen form, of not less than about 1.6 grams percubic centimeter. It has been found that zeolites which satisfy allthree of the discussed criteria are most desired for several reasons.When hydrocarbon products or by-products are catalytically formed, forexample, such zeolites tend to maximize the production of gasolineboiling range hydrocarbon products. Therefore, the preferred zeolitesuseful with respect to this invention are those having a ConstraintIndex as defined above of about 1 to about 12, a silica to alumina moleratio of at least about 12 and a dried crystal density of not less thanabout 1.6 grams per cubic centimeter. The dry density for knownstructures may be calculated from the number of silicon plus aluminumatoms per 1000 cubic Angstroms, as given, e.g., on Page 19 of thearticle ZEOLITE STRUCTURE by W. M. Meier. This paper, the entirecontents of which are incorporated herein by reference, is included inPROCEEDINGS OF THE CONFERENCE ON MOLECULAR SIEVES, (London, April 1967)published by the Society of Chemical Industry, London, 1968.

When the crystal structure is unknown, the crystal framework density maybe determined by classical pycnometer techniques. For example, it may bedetermined by immersing the dry hydrogen form of the zeolite in anorganic solvent which is not sorbed by the crystal. Or, the crystaldensity may be determined by mercury porosimetry, since mercury willfill the interstices between crystals but will not penetrate theintracrystalline free space.

It is possible that the unusual sustained activity and stability of thisspecial class of zeolites is associated with its high crystal anionicframework density of not less than about 1.6 grams per cubic centimeter.This high density must necessarily be associated with a relatively smallamount of free space within the crystal, which might be expected toresult in more stable structures. This free space, however, is importantas the locus of catalytic activity.

Crystal framework densities of some typical zeolites, including somewhich are not within the purview of this invention, are:

    ______________________________________                                                   Void       Framework                                                          Volume     Density                                                 ______________________________________                                        Ferrierite   0.28 cc/cc   1.76 g/cc                                           Mordenite    .28          1.7                                                 ZSM-5, -11   .29          1.79                                                ZSM-12       --           1.8                                                 ZSM-23       --           2.0                                                 Dachiardite  .32          1.72                                                L            .32          1.61                                                Clinoptilolite                                                                             .34          1.71                                                Laumontite   .34          1.77                                                ZSM-4 (Omega)                                                                              .38          1.65                                                Heulandite   .39          1.69                                                P            .41          1.57                                                Offretite    .40          1.55                                                Levynite     .40          1.54                                                Erionite     .35          1.51                                                Gmelinite    .44          1.46                                                Chabazite    .47          1.45                                                A            .5           1.3                                                 Y            .48          1.27                                                ______________________________________                                    

When synthesized in the alkali metal form, the zeolite is convenientlyconverted to the hydrogen form, generally by intermediate formation ofthe ammonium form as a result of ammonium ion exchange and calcinationof the ammonium form to yield the hydrogen form. In addition to thehydrogen form, other forms of the zeolite wherein the original alkalimetal has been reduced to less than about 1.5 percent by weight may beused. Thus, the original alkali metal of the zeolite may be replaced byion exchange with other suitable metal cations of Groups I through VIIIof the Periodic Table, including, by way of example, nickel, copper,zinc, palladium, calcium or rare earth metals. In practicing aparticularly desired chemical conversion process, it may be useful toincorporate the above-described crystalline zeolite with a matrixcomprising another material resistant to the temperature and otherconditions employed in the process. Such matrix material is useful as abinder and imparts greater resistance to the catalyst for the severetemperature, pressure and reactant feed stream velocity conditionsencountered in many cracking processes.

Useful matrix materials include body synthetic and naturally occurringsubstances, as well as inorganic materials such as clay, silica and/ormetal oxides. The latter may be either naturally occurring or in theform of gelatinous precipitates or gels including mixtures of silica andmetal oxides. Naturally occurring clays which can be composited with thezeolite include those of the montmorillonite and kaolin families, whichfamilies include the sub-bentonites and the kaolins commonly known asDixie, McNamee-Georgia and Florida clays or others in which the mainmineral constituent is halloysite, kaolinite, dickite, nacrite oranauxite. Such clays can be used in the raw state as originally mined orinitially subjected to calcination, acid treatment or chemicalmodification.

In addition to the foregoing materials, the zeolites employed herein maybe composited with a porous matrix material, such as alumina,silica-alumina, silica-magnesia, silica-zirconia, silica-thoria,silica-beryllia, and silica-titania, as well as ternary compositions,such as silica-alumina-thoria, silica-alumina-zirconia,silica-alumina-magnesia and silica-magnesia-zirconia. The matrix may bein the form of a cogel. The relative proportions of zeolite componentand inorganic oxide gel matrix, on an anhydrous basis, may vary widelywith the zeolite content ranging from between about 1 to about 99percent by weight and more usually in the range of about 5 to about 80percent by weight of the dry composite.

The above crystalline zeolites employed are, in accordance with thepresent invention, contacted with a solution of one or more compounds ofthe metals of Group IVB of the Periodic Chart of the Elements. ThePeriodic Chart referred to herein is that version officially approvedand adopted by the United States National Bureau of Standards (NBS) andthe International Union of Pure and Applied Chemists (IUPAC), thecontemplated elements of Group IVB being germanium (Ge), tin (Sn) andlead (Pb).

Solutions of such compounds may be in any suitable solvent which isinert with respect to the metal-containing compound and the zeolite.Non-limiting examples of some suitable solvents include water, aliphaticand aromatic hydrocarbons, alcohols, organic acids (such as acetic acid,formic acid, propionic acid and so forth), and inorganic acids (such ashydrochloric acid, sulfuric acid and nitric acid). Other commonlyavailable solvents such as halogenated hydrocarbons, ketones, ethers,etc. may be useful to dissolve some metal compounds or complexes.Generally, the most useful solvent will be found to be water. However,the solvent of choice for any particular compound will, of course, bedetermined by the nature of that compound and for that reason theforegoing list should not be considered exhaustive of all of thesuitable possibilities.

Representative germanium-containing compounds include germaniumdichloride, germanium tetrachloride, germanium dibromide, germaniumtetrabromide, germanium di- and tetra- fluorides and iodides, germaniumoxide, germanium sulfide, trimethylgermanium, triethylgermanium, andgermanium oxychloride. This listing is not to be taken as encompassingall of the utilizable germanium containing compounds. It is merelyintended to be illustrative of some of the representative metalcompounds which those in the art will find useful in practicing thedisclosed invention. The knowledgeable reader will readily appreciatethat there are numerous other known germanium salts and complexes whichwould prove useful herein to provide solutions containing germaniumsuitable for combination with the zeolite in the manner hereinafterdescribed.

Reaction of the zeolite with the treating germanium compound is effectedby contacting the zeolite with such compound. Where the treatingcompound is a liquid, such compound can be in solution in a solvent atthe time contact with the zeolite is effected. Any solvent relativelyinert with respect to the treating germanium compound and the zeolitemay be employed. Suitable solvents include water and aliphatic, aromaticor alcoholic liquid. The treating compound may also be used without asolvent, i.e. may be used as a neat liquid. Where the treating compoundis in the gaseous phase, it can be used by itself or in admixture with agaseous diluent relatively inert to the treating compound and thezeolite (such as helium or nitrogen) or with an organic solvent such asoctane or toluene. Heating of the germanium compound impregnatedcatalyst subsequent to preparation and prior to use is preferred, andheating can, if desired, be carried out in the presence of oxygen--forexample, in air. Although heating may be carried out at a temperature ofabout 150° C. or more, higher temperatures, e.g. up to about 500° C.,are preferred. Heating is generally carried out for 1-5 hours but may beextended to 24 hours or longer. While heating temperatures above about500° C. may be employed, they are generally not necessary, and attemperatures of about 1000° C. the crystal structure of the zeolitetends to deteriorate. After heating in air at elevated temperatures, andwithout being limited by any theoretical considerations, it iscontemplated that the germanium is actually present in the zeolite in anoxidized state, such as GeO₂.

The amount of germanium dioxide incorporated in the zeolite should be atleast about 0.25 percent by weight. However, it is preferred that theamount utilized comprise at least about 1.0 percent by weight,particularly when the zeolite is combined with a binder, e.g. 35 weightpercent of alumina. The amount of germanium dioxide can be as high asabout 30 percent by weight or more, depending on the amount and type ofbinder present. Preferably, the amount of oxide added to the zeolitewill be between about 1 and about 15 percent by weight.

The amount of germanium incorporated with the zeolite by reaction withelemental germanium or germanium-containing compound will depend uponseveral factors. One of these is the reaction time, i.e., the time thatthe zeolite and the germanium-containing source are maintained incontact with each other. With greater reaction times, all other factorsbeing equal, a greater amount of metal is incorporated with the zeolite.Other factors upon which the amount of germanium incorporated with thezeolite is dependent include reaction temperature, concentration of thetreating compound in the reaction mixture, the degree to which thezeolite has been dried prior to reaction with the metal-containingcompound, the conditions of drying of the zeolite after reaction withthe treating compound, and the amount and type of binder incorporatedwith the zeolite.

Oxides of tin are also effective modifying components for imparting thedesirable shape selective activity to the particular type of zeolitesdisclosed. Examples of representative tin-containing compounds suitablefor deposition of that metal on the zeolite include tin metal, tinacetate, tin bromide, tin chloride, tin fluoride, tin iodide, tinnitrate, tin oxide, tin sulfide, tin sulfur chloride, tin sulfate, andtin tartarate. As discussed above with respect to the illustrativelisting of germanium compounds, the foregoing is not to be considered asan exhaustive list of the utilizable tin salts and complexes. There arenumerous tin compounds which the foregoing will suggest to those skilledin the art as being suitable for providing the tin-containing solutionsfor treatment of the zeolite as hereinafter described.

Reaction of the zeolite with the tin compounds is accomplished insubstantially the same way as that recited above with respect to thegermanium-containing compounds. Without being limited by any theoreticalconsiderations, it is contemplated that the tin is likewise in anoxidized state, such as SnO₂.

The amount of tin oxide incorporated in the zeolite should be at leastabout 0.25 percent by weight. However, it is preferred that the amountutilized comprise at least about 1.0 percent by weight, particularlywhen the zeolite is combined with a binder, e.g. 35 weight percent ofalumina. The amount of tin oxide can be as high as about 30 percent byweight or more depending on the amount and type of binder present.Preferably, the amount of tin oxide added to the zeolite is betweenabout 1 and about 25 percent by weight.

Oxides of lead may also be employed as a modifying component. The leadoxide is contemplated as being present as PbO alone or in combinationwith other compounds of lead in an oxidized state. In all instances,regardless of the particular state of oxidation of the lead, its contentwith respect to the zeolite is computed as if it were present as PbO.Generally, the amount of PbO in the composite catalyst will be betweenabout 0.25 and about 45 weight percent, and preferably between about 1.0and about 40 weight percent, based on the weight of the composite.Reaction of the zeolite with the lead-containing compound is carried outas described above with respect to the treatment with compounds of theelement germanium. Examples of lead compounds which may be utilizedinclude lead metal, lead acetate, lead bromide, lead chloride, leadfluoride, lead iodide, lead butyrate, lead carbonate, lead bromate, leadchlorate, lead perchlorate, lead chlorite, lead citrate, lead cyanate,lead cyanide, lead enanthate, lead ethylsulfate, lead formate, leadhydroxide, lead iodate, lead periodate, lead lactate, lead laurate, leadmalate, lead oxide, lead nitrate, lead oxychloride, lead palmitate, leadphenolate, lead picrate, lead citrate, lead sulfate, lead sulfide, leadsulfite, lead tartarate, and lead thiocyanate. Again, this listing isnot intended to be exhaustive, but rather suggestive to those of skillin the art as to the kinds of metal-containing compounds useful fortreating the zeolite as herein described.

In some instances, it may be desirable to modify the crystallinezeolites by combining therewith two or more of the specified metaloxides. Thus, the zeolite may be modified by prior combination therewithof oxides of germanium and tin, oxides of germanium andlead, oxides oftin and lead or even oxides of all three elements. When suchmodification technique is employed, the respective oxides may bedeposited on the zeolite either sequentially or from a solutioncontaining suitable compounds of the elements, the oxides of which areto be combined with the zeolite. The amounts of oxides present in suchinstance are in the same range as specified above for the individualoxides, with the overall added oxide content being between about 1 andabout 40 weight percent of the composite.

A further embodiment of this invention includes additional modificationof the above metal oxide-zeolite composites with phosphorus, wherebyfrom about 0.25 weight percent to about 30 weight percent of an oxide ofphosphorus, calculated as P₂ O₅, is combined with the zeolite. Thepreferred amount of phosphorus oxide will be between about 1.0 weightpercent and about 25 weight percent, based on the weight of the treatedzeolite. The phosphorus treatment of the zeolite catalyst willpreferably be carried out before the previously described modificationthereof with Group IVB metals. Reaction of the zeolite compound with thephosphorus-containing compound is carried out essentially as describedabove with respect to the metal-containing compounds and it is preferredthat the total amount of oxides combined with the zeolite, i.e. thephosphorus oxides plus the metal oxides, fall within the approximaterange of 2 percent to 35 percent by weight, based on the weight of thetreated zeolite.

Representative phosphorus-containing compounds which may be used includederivatives of groups represented by PX₃, RPX₂, R₂ PX, R₃ P, X₃ PO,(XO)₃ PO, (XO)₃ P, R₃ P═O, R₃ P═S, RPO₂, RPS₂, RP(O)(OX)₂, RP(S)(SX)₂,R₂ P(O)OX, R₂ P(S)SX, RP(SX)₂, ROP(OX)₂, RSP(SX)₂, (RS)₂ PSP(SR)₂, and(RO)₂ POP(OR)₂, where R is an alkyl or aryl, such as a phenyl radicaland X is hydrogen, R, or halide. These compounds include primary, RPH₂,secondary, R₂ PH and tertiary, R₃ P, phosphines such as butyl phosphine;the tertiary phosphine oxides R₃ PO, such as tributylphosphine oxide,the tertiary phosphine sulfides, R₃ PS, the primary, RP(O)(OX)₂, andsecondary, R₂ P(O)OX, phosphonic acids such as benzene phosphonic acid;the corresponding sulfur derivatives such as RP(S)(SX)₂ and R₂ P(S)SX,the esters of the phosphonic acids such as diethyl phosphonate, (RO)₂P(O)H, dialkyl alkyl phosphonates, (RO)₂ P(O)R, and alkyldialkylphosphinates, (RO)P(O)R₂ ; phosphinous acids, R₂ POX, such asdiethylphosphinous acid, primary, (RO)P(OX)₂, secondary, (RO)₂ POX, andtertiary, (RO)₃ P, phosphites; and esters thereof such as the monopropylester, alkyl dialkylphosphinites, (RO)PR₂, and dialkyl alkylphosphinite,(RO)₂ PR esters. Corresponding sulfur derivatives may also be employedincluding (RS)₂ P(S)H, (RS)₂ P(S)R, (RS)P(S)R₂, R₂ PSX, (RS)P(SX)₂,(RS)₂ PSX, (RS)₃ P, (RS)PR₂ and (RS)₂ PR. Examples of phosphite estersinclude trimethylphosphite, triethylphosphite, diisopropylphosphite,butylphosphite; and pyrophosphites such as tetraethylpyrophosphite. Thealkyl groups in the mentioned compounds contain from one to four carbonatoms.

Other suitable phosphorus-containing compounds include the phosphorushalides such as phosphorus trichloride, bromide, and iodide, alkylphosphorodichloridites, (RO)PCl₂, dialkyl phosphorochloridites, (RO)₂PCl, dialkylphosphinochloridites, R₂ PCl, alkylalkylphosphonochloridates, (RO)(R)P(O)Cl, dialkyl phosphinochloridates,R₂ P(O)Cl and RP(O)Cl₂. Applicable corresponding sulfur derivativesinclude (RS)PCl₂, (RS)₂ PCl, (RS)(R)P(S)Cl and R₂ P(S)Cl.

Preferred phosphorus-containing compounds include diphenyl phosphinechloride, trimethylphosphite and phosphorus trichloride, phosphoricacid, phenyl phosphine oxychloride, trimethylphosphate, diphenylphosphinous acid, diphenyl phosphinic acid, diethylchlorothiophosphate,methyl acid phosphate and other alcohol-P₂ O₅ reaction products.

Particularly preferred are ammonium phosphates, including ammoniumhydroen phosphate, (NH₄)₂ HPO₄, and ammonium dihydrogen phosphate, NH₄H₂ PO₄.

Still another modifying treatment entails steaming of the zeolite bycontact with an atmosphere containing from about 5 to about 100 percentsteam at a temperature of from about 250° to about 1000° C. for a periodof between about 15 minutes and about 100 hours and under pressuresranging from sub-atmospheric to several hundred atmospheres. Preferably,steam treatment is effected at a temperature of between about 400° C.and about 700° C. for a period of between about 1 and about 24 hours.

Another modifying treatment involves precoking of the catalyst todeposit a coating of between about 2 and about 75, and preferablybetween about 15 and about 75, weight percent of coke therein. Precokingcan be accomplished by contacting the catalyst with a hydrocarboncharge, e.g. toluene, under high severity conditions or alternatively ata reduced hydrogen to hydrocarbon concentration, i.e. 0 to 1 mole ratioof hydrogen to hydrocarbon, for a sufficient time to deposit the desiredamount of coke thereon.

It is also contemplated that a combination of steaming and precoking ofthe catalyst under the above conditions may be employed to suitablymodify the crystalline zeolite catalyst.

Alkylation of aromatic compounds in the presence of the above-describedcatalyst is effected by contact of the aromatic with an alkylatingagent. A particulary preferred embodiment involves the alkylation oftoluene wherein the alkylating agents employed comprise methanol orother well known methylating agents or ethylene. The reaction is carriedout at a temperature of between about 250° C. and about 750° C.,preferably between about 300° C. and 650° C. At higher temperatures, thezeolites of high silica/alumina ratio are preferred. For example, ZSM-5having a SiO₂ /Al₂ O₃ ratio of 30 and upwards is exceptionally stable athigh temperatures. The reaction generally takes place at atmosphericpressure, but pressures within the approximate range of 10⁵ N/m² to 10⁷N/m² (1-100 atmospheres) may be employed.

Some non-limiting examples of suitable alkylating agents would includeolefins such as, for example, ethylene, propylene, butene, decene, anddodecene, as well as formaldehyde, alkyl halides and alcohols, the alkylportion thereof having from 1 to 16 carbon atoms. Numerous otheraliphatic compounds having at least one reactive alkyl radical may beutilized as alkylating agents.

Aromatic compounds which may be selectively alkylated as describedherein would include any alkylatable aromatic hydrocarbon such as, forexample, benzene, ethylbenzene, toluene, dimethylbenzenes,diethylbenzenes, methylethylbenzenes, propylbenzenes, isopropylbenzenes,isopropylmethylbenzenes, or substantially any mono- or di-substitutedbenzenes which are alkylatable in the 4-position of the aromatic ring.

The molar ratio of alkylating agent to aromatic compound is generallybetween about 0.05 and about 5. For instance, when methanol is employedas the methylating agent and toluene is the aromatic, a suitable molarratio of methanol to toluene has been found to be approximately 1-0.1moles of methanol per mole of toluene. Reaction is suitably accomplishedutilizing a feed weight hourly space velocity (WHSV) of between about 1and about 1000, and preferably between about 1 and about 200. Thereaction product, consisting predominantly of the 1,4-dialkyl isomer,e.g. 1,4-dimethylbenzene, 1-ethyl-4-methylbenzene, etc., or a mixture ofthe 1,4- and 1,2- isomers together with comparatively smaller amounts of1,3-dialkylbenzene isomer, may be separated by any suitable means. Suchmeans may include, for example, passing the reaction product streamthrough a water condenser and subsequently passing the organic phasethrough a column in which chromatographic separation of the aromaticisomers is accomplished.

When transalkylation is to be accomplished, transalkylating agents arealkyl or polyalkyl aromatic hydrocarbons wherein alkyl may be composedof from 1 to about 5 carbon atoms, such as, for example, toluene,xylene, trimethylbenzene, triethylbenzene, dimethylethylbenzene,ethylbenzene, diethylbenzene, ethyltoluene and so forth.

Another aspect of this invention involves the selectivedisproportionation of alkylated aromatic compounds to producedialkylbenzenes wherein the yield of 1,4-dialkyl isomer is in excess ofthe normal equilibrium concentration. In this context, it should benoted that disproportionation is a special case of transalkylation inwhich the alkylatable hydrocarbon and the transalkylating agent are thesame compound, for example when toluene serves as the donor and acceptorof a transferred methyl group to produce benzene and xylene.

The transalkylation and disproportionation reactions are carried out bycontacting the reactants with the above described modified zeolitecatalyst at a temperature of between about 350° C. and 750° C. at apressure of between atmospheric (10⁵ N/m²) and about 100 atmospheres(10⁷ N/m²). The reactant feed WHSV will normally fall within the rangeof about 0.1 to about 50. Preferred alkylated aromatic compoundssuitable for utilization in the disproportionation embodiment comprisetoluene, ethylbenzene, propylbenzene or substantially anymono-substituted alkylbenzene. These aromatic compounds are selectivelyconverted to, respectively, 1,4-dimethylbenzene, 1,4-diethylbenzene,1-4-dipropylbenzene, or other 1,4-dialkylbenzene, as appropriate, withbenzene being a primary side product in each instance. The product isrecovered from the reactor effluent by conventional means, such asdistillation to remove the desired products of benzene anddialkylbenzene, and any unreacted aromatic component is recycled forfurther reaction.

The hydrocarbon conversion processes described herein may be carried outas a batch type, semi-continuous or continuous operation utilizing afixed or moving bed catalyst system. The catalyst, after use in a movingbed reactor, is conducted to a regeneration zone wherein coke is burnedfrom the catalyst in an oxygen-containing atmosphere (e.g. air) at anelevated temperature, after which the regenerated catalyst is recycledto the conversion zone for further contact with the charge stock. In afixed bed reactor, regeneration is carried out in a conventional mannerwhere an inert gas containing a small amount of oxygen (0.5-2%) is usedto control burning of the coke so as to limit the temperature to amaximum of around 500°-550° C.

The following examples will serve to illustrate certain specificembodiments of the hereindisclosed invention. These examples should not,however, be construed as limiting the scope of the novel invention asthere are many variations which may be made thereon without departingfrom the spirit of the disclosed invention, as those of skill in the artwill recognize.

EXAMPLE 1A [Alkylation reaction with unmodified ZSM-5]

Five grams of HZSM-5 (silica/alumina mole ratio=70; 65% on aluminabinder) were placed in a quartz flow reactor and heated to varioustemperatures between 350° C. and 500° C. A mixture of toluene andmethanol, at a 4/1 molar ratio, was passed through the zeolite catalystat a weight hourly space velocity (WHSV) of 10. The reactor effluent wasmonitored and the results obtained at the various temperatures are shownbelow:

    ______________________________________                                        Temperature Percent Toluene                                                                             Percent para-isomer                                 °C.  Conversion    in Xylenes                                          ______________________________________                                        350         47.2          24.8                                                400         58.0          24.4                                                450         68.0          24.3                                                500         87.6          24.2                                                ______________________________________                                    

EXAMPLE 1B

In a similar manner, toluene was alkylated with ethylene by passingtoluene and ethylene, at WHSV of 7.0 and 0.5, respectively, over theunmodified zeolite. The results at various temperatures are shown below:

    ______________________________________                                                                 Isomer ratios of                                     Temperature                                                                              Percent Toluene                                                                             Ethyltoluene                                         °C. Conversion    p       m     o                                      ______________________________________                                        400        76.4          29.9    58.5  11.6                                   425        76.4          29.9    57.5  12.7                                   450        79.0          29.6    57.1  13.4                                   ______________________________________                                    

EXAMPLE 2 [Disproportionation reaction with unmodified ZSM-5]

Toluene was passed over a 6.0 g sample of HZSM-5 (SiO₂ /Al₂ O₃ moleratio=70; 65% on alumina binder) at a feed WHSV of 3.5-3.6 and attemperatures between 450° C. and 600° C. The results are summarized asfollows:

    ______________________________________                                        Tem-                                                                          pera-                                                                         ture         Toluene  % Selectivity, Wt.                                                                        % Para in                                   °C.                                                                         WHSV    conv., % Benzene                                                                              Xylenes                                                                              Xylene Products                           ______________________________________                                        450  3.6     7.4      43.5   55.5   24.7                                      500  3.5     20.5     44.6   53.8   24.5                                      550  3.5     38.8     48.0   48.8   24.2                                      600  3.5     49.2     54.4   41.7   24.1                                      ______________________________________                                    

EXAMPLE 3 [Preparation of Ge-modified zeolite]

A 5.0 g sample of HZSM-5 zeolite was suspended in 10 ml of GeCl₄ atambient temperature for approximately 18 hours. The zeolite wasseparated by filtration, placed in an oven at 60° C. and heated to 200°C. over a period of 2 hours. The dried zeolite was then calcined at 500°C. for 2 hours. The Ge-ZSM-5 was found to contain 3.05% germanium.

EXAMPLE 4 [Disproportionation reaction with Ge-modified zeolite]

A sample of the Ge-ZSM-5 zeolite of Example 3 was tested fordisproportionation of a toluene feed stream. The feed rate (WHSV) was3.5 and the temperature was varied between 450° C. and 600° C. Theresults are summarized as follows:

    ______________________________________                                        Temper-                                                                       ature  Toluene  % Selectivity, Wt.                                                                            % Para in                                     °C.                                                                           conv., % Benzene    Xylenes                                                                              Xylene Product                              ______________________________________                                        450    0.4      71.1       25.3   32.2                                        500    0.7      64.1       35.9   32.7                                        550    1.4      56.5       43.5   30.2                                        600    3.1      52.3       46.7   28.5                                        ______________________________________                                    

By comparison with the results obtained with an unmodified HZSM-5zeolite [Example 2], it will be seen that the selectivity to thepara-isomer in the xylene product has been increased as a result oftreating the catalyst with a germanium salt.

EXAMPLE 5 [Alkylation reaction with Ge-modified zeolite]

The Ge-ZSM-5 zeolite of Example 3 was tested for selectivity in thealkylation of aromatics at 400°-450° C. A feed stream consisting ofethylene and toluene was passed over the heated catalyst at WHSV of 0.5and 7.8, respectively, and the reactor effluent analyzed. The resultsare outlined below:

    ______________________________________                                        Temp.        Toluene      % Para Isomer                                       °C.   conv., %     in Ethyltoluene                                     ______________________________________                                        400          2.8          56.1                                                450          2.5          48.5                                                ______________________________________                                    

A very significant increase in selectivity to the para-isomer in theethyltoluene product is observed relative to that obtained with anunmodified HZSM-5 [Example 1B].

EXAMPLE 6 [Preparation of Sn-modified zeolite]

Ten grams of the ammonium form of ZSM-5 zeolite were placed in asolution of 4.8 g of liquid stannous TEN-CHEM (a tin salt of a mixtureof carboxylic acids prepared by Mooney Chemical Inc. and containing 26%Sn) dissolved in 25 ml of glacial acetic acid. The suspension was placedin an oven at about 120° C. to impregnate the zeolite with the tincompound and to remove the acetic acid. The zeolite was thereaftercalcined at 500° C. overnight. The tin content of the Sn-ZSM-5 was 10.7wt. % (calculated).

EXAMPLE 7 [Disproportionation reaction with Sn-modified zeolite]

A stream of toluene was passed over 5.0 g of the Sn-ZSM-5 zeolite ofExample 6 at WHSV of 3.5 and at temperatures of between 500° C. and 600°C. The results are summarized as follows:

    ______________________________________                                                          % Selectiv-                                                 Temperature                                                                            Toluene  ity, mole     % Para in                                     °C.                                                                             conv., % Benzene  Xylenes                                                                              Xylene Product                              ______________________________________                                        500      4.9      61.9     37.3   31.7                                        550      13.0     64.8     35.2   27.9                                        600      22.1     58.9     40.9   30.6                                        ______________________________________                                    

It is evident from the table that the level of the para-isomer in thexylene product (28-32%) exceeds the equilibrium amount of approximately24% which had been achieved with the unmodified zeolite (Example 2),thereby demonstrating increased selectivity of the modified catalyst.

EXAMPLE 8 [Preparation of Pb-modified zeolite]

Mixed 3.0 g of HZSM-5 (SiO₂ /Al₂ O₃ =70) with a solution of 4.0 g oflead acetate in 8.0 ml of water at 80° C. The mixture was maintained at80°-90° C. for 2.5 hours and then filtered to recover the zeolite. Therecovered zeolite was dried at about 90° C. for 16 hours and thencalcined at 500° C. for an additional 2.5 hours to yield 3.72 g ofPb-ZSM-5. The lead content was analyzed to be 30.4 wt. %.

EXAMPLE 9A [Alkylation reaction with Pb-modified zeolite]

Alkylation of toluene with methanol in the presence of the Pb-modifiedzeolite catalyst was carried out by passing a feed stream of toluene andmethanol (4/1 molar ratio) over the Pb-ZSM-5 of Example 8. The reactortemperature was 500° C. and the feed WHSV was 10. Toluene conversion was23.6% with a selectivity to the para-isomer in the xylene product of70.9%, as compared to a para-selectivity of 24.2% for an unmodifiedZSM-5 catalyst (Example 1A).

EXAMPLE 9B

In a similar manner, ethylene and toluene were reacted by passing thereactants (at WHSV of 0.5 and 7.0, respectively) over the Pb-ZSM-5zeolite at 400° C. Conversion of toluene was 13.4% and selectivity topara-isomer in the ethyltoluene product was 85.9%. With the unmodifiedzeolite selectivity was 29.9% under similar conditions (Example 1B).

EXAMPLE 10 [Disproportionation reaction with Pb-modified zeolite]

Toluene disproportionation to benzene and xylenes was carried out bypassing a stream of toluene over the Pb-ZSM-5 zeolite of Example 8. Thereactor temperature was 550° C. and the toluene feed rate (WHSV) was3.5. Toluene conversion was 5.7% and selectivity to para-xylene was53.9%, as compared to the equilibrium level of 24.2% para achieved inthe presence of an unmodified ZSM-5 (Example 2).

EXAMPLE 11 [Preparation of P-modified zeolite]

200 grams of ammonium-ZSM-5 (65% on alumina binder) were added to asolution of 80 g of diammonium hydrogen phosphate in 300 ml of H₂ O atabout 90° C. After standing at about 90° C. for 2 hours, the zeolite wasfiltered, dried at 90° for 2 hours and then calcined at 500° C. foranother 2 hours. The recovered P-ZSM-5 zeolite contained 3.43 wt. %phosphorus.

EXAMPLE 12A [Alkylation reaction with P-modified zeolite]

Alkylation of toluene with methanol was carried out by passing atoluene/methanol feed stream (molar ratio=4/1) over 5.0 g of the P-ZSM-5zeolite of Example 11. The feed WHSV was 10 and the reactor temperaturewas varied between 400° C. and 600° C. The results obtained aresummarized below:

    ______________________________________                                        Temperature                                                                              Percent Toluene                                                                             Percent para-isomer                                  °C. Conversion    in Xylenes                                           ______________________________________                                        400        43.6          66.6                                                 450        54.4          57.7                                                 500        70.4          53.7                                                 550        85.2          52.0                                                 600        85.2          58.0                                                 ______________________________________                                    

EXAMPLE 12B

In a similar manner, ethylation of toluene was accomplished utilizing afeed stream of toluene (WHSV=7.0) and ethylene (WHSV=0.5) in thepresence of the P-ZSM-5 catalyst at 400° C. Conversion of toluene was74.8% and selectivity to the para-isomer of ethyltoluene was 55.5%.

EXAMPLE 13 [Disproportionation reaction with P-modified zeolite]

Toluene disproportionation was tested by passing a stream of tolueneover the P-ZSM-5 catalyst of Example 11 at a feed WHSV of 3.5 and attemperatures of between 475° and 550° C. The results are summarized asfollows:

    ______________________________________                                                             % Selectiv-                                              Temperature                                                                            Toluene Conv.                                                                             ity, Mole     % Para in                                  °C.                                                                             %           Benzene  Xylene Xylenes                                  ______________________________________                                        475      14.9        52.8     47.6   39.1                                     500      27.1        53.3     45.4   35.1                                     525      37.4        56.1     42.2   32.1                                     550      44.0        60.4     37.3   30.1                                     ______________________________________                                    

EXAMPLE 14 [Preparation of Sn-P-modified zeolite]

Six grams of the P-modified ZSM-5 of Example 11 were added to a solutionof 3.0 g of metallic tin in 15 ml of concentrated HCl at ambienttemperature. After 16 hours the mixture was filtered and the zeolitedried at about 90° C. followed by calcining for 3 hours at 500° C. toyield 5.1 g of Sn-P-ZSM-5. Analysis showed the modified zeolite tocontain 14.6 wt. % tin and 1.32 wt. % phosphorus.

EXAMPLE 15A [Alkylation reaction with Sn-P-modified zeolite]

Alkylation of toluene with methanol was carried out by passing atoluene/methanol mixture (molar ratio=4/1) over 1.1 g of the Sn-P-ZSM-5catalyst prepared in Example 14. The feed WHSV was 10 and the reactortemperature was maintained at 400° C. Toluene conversion was 29.2% witha selectivity to the para-isomer of xylene of 71.5%. By comparison, theunmodified zeolite showed only 24.4% selectivity to the para-isomerunder similar conversion conditions (Example 1A) while the P-modifiedZSM-5 provided only 66.6% selectivity (Example 12A).

EXAMPLE 15B

Toluene and ethylene were reacted in the presence of the Sn-P-ZSM-5 bypassing the reactants over the catalyst at WHSV of 7.0 and 0.5,respectively, and 400° C. Conversion of toluene was 47.9% andselectivity to the para-isomer in the ethyltoluene produced was 80.6%.This is a significant increase over the 55.5% selectivity for theP-ZSM-5 of Example 12B.

EXAMPLE 16 [Disproportionation reaction with Sn-P-modified zeolite]

Disproportionation of toluene to benzene and xylenes were accomplishedby passing a toluene feed over the Sn-P-modified ZSM-5 of Example 14 at500° C. and feed WHSV of 3.5. Toluene conversion was 7.1% andselectivity to the para-isomer of xylene was 33.8%.

EXAMPLE 17 Preparation of Pb-P-modified zeolite]

Added 6.0 g of the P-modified zeolite prepared in Example 11 to asolution of 5.0 g lead acetate in 10 ml H₂ O at about 80° C. The mixturewas maintained at 80°-90° C. for 2 hours, then filtered and the zeolitedried at 90° C. After calcining at 500° C. for 1.2 hours 7.33 g ofPb-P-ZSM-5 were recovered. Analysis showed the lead content of themodified zeolite to be 21.1% and that of phosphorus to be 3.02%.

EXAMPLE 18A [Alkylation reaction with Pb-P-modified zeolite]

Alkylation of toluene with methanol was carried out in the presence ofthe Pb-P-ZSM-5 zeolite of Example 17. The toluene/methanol feed stream(4/1 molar ratio) was brought into contact with the modified zeolite atWHSV of 10 and a temperature of 500° C. Toluene conversion was 17.6% andselectivity to the para-isomer of xylene was 94.5%, in comparison to a53.7% selectivity obtained with the P-ZSM-5 alone (Example 12A).

EXAMPLE 18B

Ethyltoluene was produced by alkylation of toluene with ethylene in thepresence of the Pb-P-ZSM-5 zeolite. Reactor temperature was 400° C. andthe reactant feed rate (WHSV) was 7.0 for toluene and 0.5 for ethylene.Conversion of toluene was 4.6% and selectivity to para-ethyltoluene was98%. This is in comparison to a para-selectivity of 55.5% for theP-modified ZSM-5 under the same conditions of reaction (Example 12B).

EXAMPLE 19 [Disproportionation reaction with Pb-P-modified zeolite]

Toluene disproportionation was carried out by passing a toluene feedover a sample of the Pb-P-modified ZSM-5 of Example 17. The reactortemperature was maintained at 550° C. and the toluene feed rate (WHSV)was 3.5. Conversion of toluene was 4.1% with a selectivity of 91.4% tothe para-isomer of xylene. Under similar conditions of reaction, theP-ZSM-5 zeolite gave only 30.1% selectivity to the para-isomer.

EXAMPLE 20 [Preparation of Ge-P-modified zeolite]

Five grams of a P-modified ZSM-5 zeolite, similar to that described inExample 11, were mixed with 25.0 g of GeCl₄ and the mixture gentlyrefluxed for 18.25 hours. After cooling, the zeolite was removed byfiltration and placed in an oven at 60° C. The temperature was graduallyincreased to 250° C. over a period of 1 hour and then held at 250° C.for 2 hours. The dried Ge-P-ZSM-5 was then calcined at 500° C. for 2hours. Germanium content of the modified zeolite was 2.96 wt. % andphosphorus was 3.34 wt. %.

EXAMPLE 21A [Alkylation reaction with Ge-P-modified zeolite]

Toluene was alkylated with methanol by passing a feed stream of tolueneand methanol (molar ratio=4/1) over 2.2 g of the Ge-P-ZSM-5 zeolite ofExample 20. The feed WHSV was 11 and the reactor temperature was variedbetween 400° C. and 600° C. The results obtained at various temperaturesare summarized below:

    ______________________________________                                        Temperature   Toluene     % Para-isomer                                       °C.    conv., %    in Xylenes                                          ______________________________________                                        400           42.0        80.8                                                500           62.8        72.0                                                600           78.4        70.5                                                ______________________________________                                    

Under similar reaction conditions, the ZSM-5 which had been modifiedwith only phosphorus demonstrated a para-selectivity of 52-67% (Example12A).

EXAMPLE 21B

In a similar manner, toluene and ethylene were reacted in the presenceof the Ge-P-ZSM-5 to produce ethyltoluenes. Reaction temperature was400° C. and the feed WHSV was 7.8 and 0.5, respectively. Conversion oftoluene was 88% while selectivity to the para-isomer in the ethyltolueneproduct was 84.1%.

EXAMPLE 22 [Disproportionation reaction with Ge-P-modified zeolite]

Toluene disproportionation to benzene and xylenes was carried out bypassing a toluene feed over the Ge-P-ZSM-5 zeolite of Example 20 at WHSVof 3.5 and temperatures of between 450° C. and 600° C. The results aresummarized as follows:

    ______________________________________                                        Temperature                                                                             Toluene   Selectivity, %                                                                              % Para in                                   °C.                                                                              conv., %  Benzene   Xylene                                                                              Xylenes                                   ______________________________________                                        450       4.0       45.6      54.0  54.4                                      500       9.8       44.4      55.2  49.9                                      550       19.5      45.8      53.8  45.4                                      600       28.4      49.4      49.3  43.7                                      ______________________________________                                    

EXAMPLE 23 [Disproportionation reaction with unmodified ZSM-11]

A 1.0 g portion of unmodified ZSM-11 zeolite (silica to alumina moleratio=70) was placed in a quartz flow reactor and heated to temperature.Toluene was passed over the zeolite at WHSV of 3.8 and varioustemperatures between 400° C. and 600° C. The results are as follows:

    ______________________________________                                        Temper-                                                                              Toluene                                                                ature  Conv.    % Selectivity, moles                                                                         % Para in                                      °C.                                                                           mole %   Benzene   Xylenes                                                                              Xylene Products                              ______________________________________                                        400     3.0     51.7      47.8   24.3                                         450     8.7     48.1      50.7   24.1                                         500    21.7     49.0      48.9   23.7                                         550    39.1     53.7      42.6   23.7                                         600    49.9     58.6      36.8   23.4                                         ______________________________________                                    

EXAMPLE 24A [Alkylation reaction with unmodified ZSM-11]

A toluene/methanol feed stream, having a 4/1 molar ratio of therespective reactants, was passed over unmodified HZSM-11 zeolite (SiO₂/Al₂ O₃ =70) at 400°-600° C. and a feed WHSV of 10. The results areshown below:

    ______________________________________                                        Temperature                                                                             Percent Toluene                                                                             Percent Para Xylene                                   °C.                                                                              Conversion    in Xylenes                                            ______________________________________                                        400       67.6          23.4                                                  500       90.4          24.0                                                  600       157.2         22.7                                                  ______________________________________                                    

EXAMPLE 24B

A toluene/ethylene feed stream was similarly brought into contact withthe unmodified HZSM-11. The feed WHSV was 7.5 and 0.55, respectively,and the temperature of reaction 400°-450° C. The results are summarizedbelow:

    ______________________________________                                                               Isomer ratios of                                       Temperature                                                                              % Toluene   Ethyltoluene                                           °C. Conversion  p        m      o                                      ______________________________________                                        400        80.2        27.3     58.4   14.3                                   450        81.9        27.2     57.9   14.9                                   ______________________________________                                    

EXAMPLE 25 Preparation of Pb-modified ZSM-11]

Added 1.5 g of HZSM-11 zeolite (SiO₂ /Al₂ O₃ ratio=70) to a solution of3.0 g lead acetate in 6 ml H₂ O at about 60° C. The mixture wasmaintained at 80°-90° C. for 1 hour, then filtered and the zeolite driedfor 16 hours at 90° C. The dried zeolite was thereafter calcined at 500°C. for 2.0 hours to yield 2.14 g of Pb-ZSM-11. The lead content of themodified zeolite was 36.7 wt. %.

EXAMPLE 26A [Alkylation reaction with Pb-modified ZSM-11]

Alkylation of toluene with methanol was catalyzed by the Pb-ZSM-11zeolite of Example 25 by passing a feed stream of toluene and methanol(4/1 molar ratio) over the modified zeolite at feed WHSV of 10 and areactor temperature of 500° C. Toluene conversion was 52.0% withselectivity to the para-isomer in the xylene product of 42.8%. This inin marked contrast to the 24.0% para-selectivity achieved by theunmodified HZSM-11 under similar conditions of reaction (Example 24A).

EXAMPLE 26B

In a similar manner, ethyltoluene was produced by alkylation of toluenewith ethylene in the presence of the Pb-ZSM-11 zeolite of Example 25.The feed WHSV was 3.4 of toluene and 0.5 for ethylene and reactortemperature was 400° C. Conversion of toluene was 5.8% with a 73.9%selectivity to the para-isomer of ethyltoluene.

EXAMPLE 27 [Disproportionation reaction with Pb-modified ZSM-11]

Toluene disproportionation was carried out by contacting a toluene feedwith the Pb-ZSM-11 zeolite of Example 25 at 550° C. and WHSV of 3.5.Toluene conversion was 1.2% and selectivity to the para-isomer of xylenewas 42.9%.

It is to be understood that the foregoing examples are intended to bemerely illustrative of certain specific embodiments of the disclosedinvention. As those of skill in the art will readily appreciate, thereare many variations which may be made on these specific embodimentswithout departing from the spirit of the invention described herein andsuch variations are clearly to be encompassed within the ambit of thefollowing claims.

We claim:
 1. A process for conversion of organic compounds, said processcomprising contacting said organic compounds with a crystalline zeolitecatalyst at a temperature of between about 250° C. and about 750° C. anda pressure within the approximate range of 10⁵ N/m² to 10⁷ N/m², saidzeolite being characterized by a silica to alumina mole ratio of atleast 12 and a constraint index within the approximate range of 1 to 12,said zeolite having undergone prior modification by treatment with oneor more compounds containing metal elements of Group IVB to depositthereon at least 0.25 weight percent of such metal element.
 2. Theprocess of claim 1 wherein said temperature is between 300° C. and 650°C.
 3. The process of claim 1 wherein said metal element of Group IVB ischosen from the group consisting of germanium, tin and lead.
 4. Theprocess of claim 1 wherein said metal element is germanium.
 5. Theprocess of claim 4 wherein said germanium comprises between 1 and 15weight percent of the modified zeolite catalyst.
 6. The process of claim1 wherein said metal element is tin.
 7. The process of claim 6 whereinsaid tin comprises between 1 and 25 weight percent of the modifiedzeolite catalyst.
 8. The process of claim 1 wherein said metal elementis lead.
 9. The process of claim 8 wherein said lead comprises betweenabout 1 and 40 weight percent of the modified zeolite catalyst.
 10. Theprocess of claim 1 wherein said zeolite is also modified by treatmentthereof with a compound of the element phosphorus to deposit thereon atleast 0.25 weight percent of phosphorus.
 11. The process of claim 10wherein said zeolite has deposited thereon both phosphorus andgermanium.
 12. The process of claim 10 wherein said zeolite hasdeposited thereon both phosphorus and tin.
 13. The process of claim 10wherein said zeolite has deposited thereon both phosphorus and lead. 14.The process of claim 1 wherein said zeolite is admixed with a bindertherefor.
 15. The process of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,12, 13 or 14 wherein said conversion comprises the alkylation of anaromatic compound by contacting said compound with an alkylating agentto produce dialkylbenzene compounds wherein the 1,4-dialkylbenzeneisomer is present in excess of its normal equilibrium concentration. 16.The process of claim 15 wherein said zeolite is chosen from the groupconsisting of ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38 and ZSM-48.17. The process of claim 15 wherein said zeolite is ZSM-5.
 18. Theprocess of claim 15 wherein said zeolite is ZSM-11.
 19. The process ofclaims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14 wherein saidconversion comprises the transalkylation of aromatic compounds toproduce dialkylbenzene compounds wherein the 1,4-dialkylbenzene isomeris present in excess of its normal equilibrium concentration.
 20. Theprocess of claim 19 wherein said zeolite is chosen from the groupconsisting of ZSM-5, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-38 and ZSM-48.21. The process of claim 19 wherein said zeolite is ZSM-5.
 22. Theprocess of claim 19 wherein said zeolite is ZSM-11.
 23. The process ofclaims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14 wherein saidconversion comprises disproportionation of alkylbenzenes to producebenzene and dialkylbenzenes in which the proportion of1,4-dialkylbenzene isomer is in excess of its normal equilibriumconcentration.
 24. The process of claim 23 wherein said zeolite ischosen from the group consisting of ZSM-5, ZSM-11, ZSM-12, ZSM-23,ZSM-35, ZSM-38 and ZSM-48.
 25. The process of claim 23 wherein saidzeolite is ZSM-5.
 26. The process of claim 23 wherein said zeolite isZSM-11.